Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J133/00—Adhesives based on homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by only one carboxyl radical, or of salts, anhydrides, esters, amides, imides, or nitriles thereof; Adhesives based on derivatives of such polymers
  • C09J133/04—Homopolymers or copolymers of esters
  • C09J133/06—Homopolymers or copolymers of esters of esters containing only carbon, hydrogen and oxygen, the oxygen atom being present only as part of the carboxyl radical
• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09J—ADHESIVES; NON-MECHANICAL ASPECTS OF ADHESIVE PROCESSES IN GENERAL; ADHESIVE PROCESSES NOT PROVIDED FOR ELSEWHERE; USE OF MATERIALS AS ADHESIVES
  • C09J151/00—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers
  • C09J151/003—Adhesives based on graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Adhesives based on derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
  • C08L2666/04—Macromolecular compounds according to groups C08L7/00 - C08L49/00, or C08L55/00 - C08L57/00; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L2666/00—Composition of polymers characterized by a further compound in the blend, being organic macromolecular compounds, natural resins, waxes or and bituminous materials, non-macromolecular organic substances, inorganic substances or characterized by their function in the composition
  • C08L2666/02—Organic macromolecular compounds, natural resins, waxes or and bituminous materials
  • C08L2666/24—Graft or block copolymers according to groups C08L51/00, C08L53/00 or C08L55/02; Derivatives thereof
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L51/00—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L51/003—Compositions of graft polymers in which the grafted component is obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers grafted on to macromolecular compounds obtained by reactions only involving unsaturated carbon-to-carbon bonds

Definitions

• the invention relates to emulsion copolymer blends intended for use as adhesives, in particular packaging applications.
• Emulsion copolymers are obtained by copolymerising monomers in an emulsified reaction medium.
• the emulsion copolymer blends of the invention are of value when bonding filmic substrates formed from polymers and having smooth hydrophobic surfaces, an example is polypropylene.
• Adhesive compositions comprising a copolymer emulsion of a vinyl alkanoate/ethylene copolymer are well characterised for use in lamination processes.
• Laminating adhesives are required to provide stable adhesion over a range of temperatures but there is a general problem in obtaining suitable adhesion to filmic surfaces. These surfaces are smooth and have hydrophobic properties, an example is polypropylene but polyethylene is also required to be bonded.
• One article in which such bonding is required is laminates when the filmic substrate is bonded to a second substrate.
• An example of the second substrate is a cellulosic based substrate, eg paper or board, prepared from cellulosic fibres as a component.
• the cellulosic substrate will usually be non woven and may include other fibres, for example plastics, eg polyamide, polyester.
• the desired adhesive compositions may contain other components, for example fillers, surfactants, solvents, tackifying resins, dispersants and antifoam agents.
• the invention provides an adhesive composition for filmic surfaces based on a vinyl alkanoate/ethylenic hydrocarbon polymer having a grafted polyvinyl alcohol colloidal stabiliser and blended with a carboxylated acrylate copolymer emulsion.
• This composition provides a good range of adhesive properties on filmic surfaces without the requirement to have plasticisers or thickeners added to the composition.
• compositions of the invention comprise
• the content of vinyl alkanoate in the copolymer (i) will usually be in the range 70% to 95% by weight.
• This adhesive blend composition will preferably have a viscosity in the range 20 to 60 poise as measured on a Brookfield viscometer and the preferred pH of the blend is 6.0 to 7.5 to provide the appropriate stability of the composition.
• Polyvinyl alcohol is used as a protective colloid and is introduced into the reaction medium in a manner which ensures it is grafted onto the copolymer particles.
• the initiations conditions, surfactants present, concentration of PVA at initiation and during reaction, type of PVA and pH will be reaction characteristics which control the grafting of the PVA.
• Polyvinyl alcohols having a degree of hydrolysis from 70% to 99.8% are usable but the preferred range is from 85% to 95%.
• the average molecular weight of the PVA is chosen to give the desired final product viscosity.
• the amount of PVA present in the reaction medium is usually about 1% to about 10% by weight of the monomers with the lower level determining the effect obtained and the effect being unlikely to increase above the upper level. In particular the lower levels are usable if other stabilisers are present.
• the presence of the grafted polyvinyl alcohol was essential to provide the dried or partially dried copolymer film with suitable redispersability in water; this is of value in cleaning machinery used to apply the adhesive and is usually termed "easy-clean".
• the grafted polyvinyl alcohol is also necessary to give heat resistances.
• the preferred vinyl alkanoate is vinyl acetate but vinyl propionate and butyrate are also usable.
• the preferred ethylenic hydrocarbon is ethylene but propylene, butene and isobutylene may be used.
• the lower level of 5% ethylenic hydrocarbon is required to give the desired properties while above 30% the heat resistance of the copolymer reduces.
• At least about 5% by weight solids of the carboxylated acrylate will be required to provide the desired properties while above about 15% the cost effectiveness of this blended copolymer emulsion reduces.
• the upper level of carboxylated acrylate copolymer will be about 10% by weight solids.
• Other monomers may be present at low, ie up to about 10% by weight of the total monomer content, in the VA/E emulsion.
• Examples are acrylates, methacrylates, higher vinyl esters, vinyl halides and functional monomers, eg carboxylic acids, and multifunctional monomers, eg triallyl cyanurate and di-allyl phthalate, although care must be taken in their selection because these third monomers can interfere with polyvinyl alcohol grafting or ethylene uptake.
• carboxylic monomers used in the acrylate emulsion component are acrylic acid and methacrylic acid.
• the major monomer components will be (meth)acrylates, for example methyl methacrylate, ethyl methacrylate, n-butyl acrylate and other alkyl acrylates.
• the major monomers are selected to provide a Tg in the range -20°C to +20°C preferably -5°C to +15°C.
• the properties of the adhesive compositions were measured by the following procedures.
• This example describes the preparation of a polyvinyl alcohol (PVA) stabilised copolymer of vinyl acetate and ethylene wherein the polyvinyl alcohol is grated to the polymer.
• PVA polyvinyl alcohol
• a polyvinyl alcohol solution was made consisting of: 64.8 parts of 88% hydrolysed PVA at a molecular weight of 29,000 and 25.2 parts of 88% hydrolysed PVA at a molecular weight of 98,000 in 800 parts of water containing 5 ppm ferric ion as the polymerisation catalyst promoter.
• the pH of this solution was adjusted to 3.0-3.5 with a 50% solution of tartaric acid before heating in a pressure-resistant reactor to 30°C.
• the batch temperature was maintained at 75°C during the polymerisation process.
• This copolymer had the monomer amounts of:
• This example describes the preparation of a carboxylated copolymer of methyl methacrylate and n-butyl acrylate.
• the polymer was produced from a monomer composition (A) of:
• n-dodecyl mercaptan 10.5 g Into a stirred reactor of 2.0 litre capacity was added water 360 g. which was purged with nitrogen for 30 mins whilst heating to 85-87°C.
• a surfactant solution (B) was prepared consisting of:
• An initiator solution (C) was prepared consisting of:
• monomer mixture (A) including n-dodecyl mercaptan, surfactant solution (B) and initiator solution (C) were added continuously at a uniform rate for 4 hrs whilst maintaining the internal temperature in the range 84-86°C.
• Initiator solutions (D) and (E) were added to the reactor at the end of the 10 minutes period, and the batch held at 85°C for a further 30 minutes.
• the pH of the final emulsion is adjusted from pH 1.5 to 5.0 using ammonia solution such that the final solid content of the product does not drop below 55%.
• the acrylic copolymer emulsion described above is prepared at approximately 56% non-volatile content (56.9%) and at a pH of 1.5. It had a Tg of -5°C.
• VA/E basic vinyl acetate/ethylene copolymer emulsion and its blend were tested for characteristics, both in-use and adhesion.
• VA/E emulsion having grafted polyvinyl alcohol has the desired adhesive and in-use properties, except for polypropylene adhesion.
• Addition of the carboxylated acrylate emulsion improves the polypropylene adhesion while maintaining the other properties at satisfactory levels.

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• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Adhesives Or Adhesive Processes (AREA)

Applications Claiming Priority (2)

Publications (1)

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Citations (2)

• 1991
  • 1991-05-22 EP EP91304647A patent/EP0459698A1/fr not_active Withdrawn

Patent Citations (2)

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